Development of high-performance Schottky diode detector in the submillimeter wave region

本研究的目的是实现一种高性能的亚毫米波(SMMW)铂/砷化镓肖特基二极管(SD)探测器，该探测器具有高灵敏度和良好的机械稳定性。该探测器由反向蜂窝SD、晶须天线和射频微带滤波器组成，采用光刻技术制作。关于反向蜂窝SD的制作工艺，我们成功地发展了ECR等离子体各向异性刻蚀技术，在厚度为4000A的SiO_2上制作了直径为0.17微米、间距为0.5微米的点阵图形，而不破坏底层的GaAs外延层。这对于获得低噪声SD是必不可少的，该技术也将适用于其他半导体器件的制造工艺。制作了晶须天线和射频微带滤波器，并对其尺寸进行了验证。我们计划完成反向蜂窝SD，制作探测器支架，组装这些元件，然后测量探测器的特性。在探测器的测试和表征中，我们成功地研制了具有高稳定输出功率的光泵亚毫米波激光器和传输损耗为0.2dB的双工器。在研制过程中，我们发现了以CH2F2气体为激光介质的一条新的激光谱线(波长：746.4微米)。我们进一步尝试利用半导体中激光产生的自由载流子来调制毫米波辐射。用激光脉冲照射高阻硅或砷化镓晶片，调制了214.6微米的辐射。实现了上升沿6毫微秒的亚毫米波开关和持续时间为10毫微秒的亚毫米波短脉冲的产生。这种光开关技术对测量毫米波探测器的速度非常有用，可以应用于分子光谱和固体物理等领域。

The aim of the research is to realize a high-performance Pt/GaAs Schottky Diode (SD) detector operated in the submillimeter wave (SMMW) region with characteristics of high-sensitivity and good mechanical stability. The detector consists of reverse honeycomb SD,whisker antenna and RF microstrip filter which are fabricated using photolithographic technique. Concerning a fabrication process of reverse honeycomb SD,we have successfully developed an ECR plasma anisotropic etching technique to make a dot-matrix pattern (diameter : 0.17mum, pitch : 0.5mum) on SiO_2 with thickness of 4000A without damaging the underlying GaAs epi-layr. This is essential to obtain low-noise SD and the technique would also be applicable to fabrication processes for other semiconductor devices. We also made the whisker antenna and RF microstrip filter and have verified their dimensions as designed. We plan to complete the reverse honeycomb SD,make the detector mount, assemble these components and then measure the detector characteristics.For the testing and characterization of the detector we have succeeded in developing an optically pumped SMMW laser with highly stable output power and a diplexer with propagation loss of 0.2dB.In the course of the development we have discovered a new lasing line (wavelength : 746.4mum) when using CH_2F_2 gas as a lasing media. We further tried to modulate the SMMW radiation by laser-produced free carriers in semiconductors. Modulation of 214.6mum radiation was carried out by irradiating high-resistivity silicon or GaAs wafers with optical pulses from a Nd : YAG laser. We have achieved SMMW switching with rise time of 6nsec and generation of SMMW short pulses with duration of 10nsec. This optical switching technique is very useful for measuring the speed of SMMW detectors and could be applied to fields like molecular spectroscopy and solid-state physics.